Microsoft released the first public beta (Beta 2) of Office 2007 today. I've been using this since the first alpha and I can tell you it's a marked improvement.
If you haven't had the opportunity to test previous builds, grab this today. The calendar in Outlook 2007 alone is worth the upgrade, and if you use OneNote this is a must-have upgrade.
Update: Vista Beta 2 is out too (if you're on the beta or have an MSDN subscription). The only problem is that you can't install Office 2007 Beta 2 on Vista. Ooops.
I was having trouble using the new downloader here as well. I already have .Net 1.1 installed but the installer tries to install it anyway (and fails in the process). Now, whatever site they are delivering the content through seems to be down too. I get redirected here: "Due to high demand the site is temporarily unavailable. Please try it again later."
What a disaster. Hopefully I'll be able to get this when I get home.